Centrifugal mechanism and switch assembly



July 21, 1970 v E. J. SCHAEFER CENTRIFUGAL MECHANISM AND SWITCH ASSEMBLY 2 SheetS- -Shee-t 1 Filed May 29, 1967 87 fnz/enz a 7"." Fdwcz rd Jfidzaefm y 1, 1970 E. J. SCHAEFER 3,521,496

. CENTRIFUGAL MECHANISM AND SWITCH ASSEMBLY Filed May 29, 1967 2 Sheets- Sheet z United States Patent Int. Cl. 601 3/18 U.S. c1. 7s-s3s 4 Claims ABSTRACT OF THE DISCLOSURE This disclosure deals with an assembly of a centrifugal mechanism and an electric switch for use with an electric motor, the mechanism being rotated by the motor and the switch being electrically connected to cut out a start winding of the motor at a predetermined motor speed. The centrifugal mechanism includes two inexpensively molded parts, one of the parts being secured to the motor shaft and the other part being hinged to the first mentioned part. Hinge pins and springs connect the two parts. The parts are assembled off the motor shaft, and once the assembly is fastened to the motor shaft, an interlocking relation between the two parts and the hinge pins prevents disassembly. The switch includes a molded case and two contact carrying members, one of the two mem bers, in addition to carrying a contact, including a portion which serves as a spring and another portion which engages the centrifugal mechanism.

Certain types of electric motors have a running winding, a starting winding, and a motor speed responsive apparatus including a switch designed to connect the starting winding to a power supply only at motor speeds below a predetermined speed. Usually, the switch is closed at standstill and open when the motor is operating above the predetermined speed, and the switch automatically recloses when the motor speed falls to the predetermined speed.

An electric motor including an assembly of this character is disclosed in E. I. Schaefer Pat. No. 3,244,832 issued Apr. 5, 1966. The centrifugal mechanism includes a first part secured to the motor shaft and a second part pivotally connected to the first part by parallel links. A pair of springs hold the second part in an at rest position when the motor is deenergized but the second part swings radially and axially, due to the centrifugal force, relative to the first part to a running position when the motor is energized and reaches running speed. The switch is mounted adjacent the centrifugal mechanism, and the axial movement of the second part, as it shifts between the at rest and running positions, actuates the switch.

The assembly disclosed in the foregoing Schaefer Pat. No. 3,244,832 works very well but it is especially suited for use with relatively large size motors. This is true because the assembly is relatively large and expensive and has a relatively large current rupturing capacity. For smaller motors, a smaller and less expensive construction is desirable. In addition, the switch of an assembly for a small size motor may need only a relatively small force to actuate it.

In accordance with the present invention, a centrifugal mechanism and switch assembly is provided, the mechanism comprising primarily two molded parts. One part is secured to the motor shaft and the other part is swingably connected to the first part by a pair of double hinge pins or links and by a pair of springs. No machining or drilling of the two molded parts is required and the two molded parts are held together in interlocking assembled relation with the pins when installed on a motor shaft.

3,521,496. Patented July 21, 1970 "ice The switch of the assembly comprises a molded case which encloses a stationary member and a movable member, each of the members carrying a contact. In addition to carrying a contact, the movable member includes an actuating arm portion and a spring portion. Due to the novel arrangement of the switch elements, the switch may be easily assembled and permits a relatively long overtravel of the actuating arm portion, and the switch may be actuated without excessive actuating force. Further, the switch is mounted in the motor such that it may be easily removed for servicing or replacement after failure, without disassembly of the motor.

Objects and advantages of the invention will be apparent from the following description taken in conjunction with the accompanying figures of the drawings, in which:

FIG. 1 is a view partially in section of a motor including a centrifugal mechanism and switch assembly embodying the invention;

FIG. 2 is a fragmentary end elevational view of the motor;

FIG. 3 is an enlarged fragmentary view showing the centrifugal mechanism of the assembly when in an at rest position;

FIG. 4 is a view similar to FIG. 3 but showing the mechanism in a running position;

FIG. 5 is a view taken on the line 5-5 of FIG. 3;

FIG. 6 is a sectional view taken on the line 6-6 of FIG. 3;

FIG. 7 is a sectional view taken on the line 77 of FIG. 3;

FIG. 8 is a view of the mechanism during the assembly thereof;

FIG. 9 is an enlarged elevational view of the switch of the assembly;

FIG. 10 is a sectional view taken on the line 10-10 of FIG. 9;

FIG. 11 is an elevational view taken on the line 1111 of FIG. 9;

FIG. 12 is an enlarged side elevational view of a part of the switch;

FIG. 13 is a plan view of the part shown in FIG. 12;

FIG. 14 is a side elevational view of another part of the switch; and

FIG. 15 is a plan view of the part shown in FIG. 14.

In greater detail, FIGS. 1 and 2 illustrate an electric motor 20 including a cylindrical stator shell 21 and two end bells 22 and 23 which are secured to and close the ends of the shell. A stator assembly 24 is secured to the inner periphery of the shell 21, and a rotor 26 including a shaft 27 is positioned within the stator and rotatably mounted on the end bells 22 and 23. A foot or mounting bracket 28 is secured to the lower side of the shell 21 for securing the motor in a fixed position. The right hand end, as seen in FIG. 1, of the shaft 27 is supported by a bearing assembly (not shown) in the end bell 23, and the left hand end of the shaft 27 is rotatably mounted in the end bell 22 by means of a bearing assembly 29.

The motor 20 further includes an assembly of a centrifugal mechanism 41 mounted on the rotor shaft 27 between the rotor 26 and the ball bearing 29, and a switch 40 mounted on the end bell 22 in position where it may be actuated by the centrifugal mechanism 41. With reference to FIGS. 3 to 8, the centrifugal mechanism 41 comprises a hub part 42 and a track part 43, the two parts 42 and 43 being swingably connected together by a pair of U-shaped hinge pins 44 and 45.

With reference to FIG. 7, the hub part 42 is a one piece molded plastic member having an opening 46 formed therein, the rotor shaft 27 extending through the opening 46 and being secured to the part 42 as by a press fit. On

one side of the shaft 27, a pair of laterally spaced hinge lugs 47 and 48 are formed on the part 42, and aligned holes 49 are formed through the lugs 47 and 48, the holes receiving one arm of the U-shaped hinge pin 44. On the opposite side of the shaft from the lugs 47 and 48 is provided another pair of hinge lugs 51 and 52, the lugs 51 and 52 having aligned holes 53 formed therethrough which receive an arm of the U-shaped hinge pin 45. As shown in FIG. 7, approximately one-half the hub part 42 on the side adjacent the lugs 51 and 52 is enlarged as compared to the other side, for the purpose of proper balancing of the entire centrifugal mechanism. Such enlargement is achieved by forming relatively thick radially extending wing portions 54 on this side of the hub part 42.

In addition to the hinge pin lugs and the wings, a pair of laterally spaced hook-shaped ears 56 are formed on the hub part 42, spaced laterally outwardly from the lugs 51 and 52. As shown in FIG. 3, the ears 56- extend longitudinally toward the track part 43 and then curve radially outwardly from the shaft 27 to form a hook and the lat erally inner sides of the ears are spaced from the lugs 51 and 52 a distance which is slightly greater than the thickness of the hinge pins, as shown in FIG. 7. These ears 56 perform the dual function of hook supports for an end of a pair of tension springs 58 and abutments which hold the parts 42 and 43 and the pins 44 and 45 in assembled relation while on the shaft 27, as will be explained hereafter. The track part 53 also comprises a molded plastic member (FIG. 6) having an elongated opening 61 formed therethrough through which the shaft 27 extends. The elongation of the opening 61 is in the direction of the desired swinging movement permitted by the pins 44 and 45. While the track part 43 may be a one piece molded plastic member, a weight 62 (FIG. 6) may be provided within the member, the part 43 being molded around the weight. On the side of the track part 43 facing the hub part 42, there is provided a pair of laterally spaced hinge pin lugs 63 and 63a which have holes 64 formed therethrough, the holes 64 receiving one arm of the hinge pin 44. A second pair of hinge pin lugs 66 and 66a having a hole 67 formed therethrough is also provided for one arm of the other hinge pin 45. The two pairs of lugs on the part 43 are laterally spaced on opposite sides of the shaft 27 (FIG. 8) and are spaced in the direction of elongation of the opening 61.

The track part 43 also has a pair of hook-shaped ears 71 formed thereon laterally spaced from the hinge pin lugs 63 and 63a for the same purpose as the ears 56. As shown in FIGS. 3 and 5, the two tension springs 58 are connected between the ears 56 and 71, one of the springs 58 being on each side of the shaft 27 The hinge pins 44 and 45 are made of metal wire and are bent into the shape of a U (FIG. The arms of the pin 44 are positioned in the holes 49 and 64 of the associated hinge pin lugs, and the arms of the pin 45 are positioned in the holes 53 and 67 of the associated hinge pin lugs. The axes of the holes 49, 64, 53 and 67 and the arms of the pins are normal to the direction of elongation of the opening 61, so that the track part 43 may swing relative to the hub part 42 in the direction of elongation of the opening 61. When the mechanism is in the at rest position shown in FIG. 3, the lugs 47 and 48 are longitudinally aligned with the lugs 63 and 63a, and the lugs 51 and 52 are longitudinally aligned with the lugs 66 and 66a. The center portions of the pins 44 and 45 also extend longitudinally. The tension springs 58 connected at their ends to the ears 56 and 71, extend in the direction of elongation of the opening 61 and tend to hold the track part in the position shiwn in FIGS. 3 and 6 where the side 6111 of the opening 61 bears against the shaft 27. The location of the hinge pin lugs on the two parts relative to the side 61a is such. that the lugs are longitudinally aligned, as previously explained.

The weight distribution in the radial direction, of the track part 43 is such that the part 43 tends to move radial- Cir 1y due to centrifugal force when the mechanism 41 is rotated, the direction of such radial movement being in the direction of elongation of the opening 61 and against the force of the tension springs 58. The two hinge pins 44 and 45 cause the part 43 to swing radially and also axially toward the hub part 42 when the shaft 27 and the mechanism are rotated at above a predetermined speed, the part 43 being held in planes parallel to the part 42 and normal to the shaft 27. The extent of such swinging movement is determined by the location of the side 61b of the opening 61, and FIG. 4 shows the relative positions of the parts 42 and 43 when the side 61b engages the shaft 27, referred to herein as the running position.

To assemble the members of centrifugal mechanism and then to mount the mechanism on the shaft 27, the two parts 42 and 43 are first positioned as shown in FIG. 8, with the hinge pin lugs of the two parts facing each other and the track part 43 offset relative to the track part 43 in the direction which is opposite the direction of movement due to centrifugal force. It will be noted in FIGS. 3 and 4 that, when the mechanism is in the at rest and running positions, one of the ears 71 0f the part 43 overlies the center portion of the hinge pin 44 and one of the ears 56 of the part 42 overlies the center portion of the hinge pin 45, the ears thus preventing the pins from being withdrawn from the respective holes 64 and 67. However, before the parts 42 and 43 are on the shaft 27, the part 43 is shifted relative to the part 42 to the positions shown in FIG. 8, and the ears no longer overlie the center portions of the hinge pins and the hinge pins may be freely inserted into or removed from the holes in the hinge pin lugs. This can happen only when parts 42 and 43 are off the shaft 27. Therefore, when assembling the mechanism the parts 42 and 43 are first moved to the position shown in FIG. 8 and while in this position, the arms of the pin 44 are inserted into the holes 49 and 64 and the arms of the other hinge pin 45 are inserted into the holes 53 and 67. Due to the offset of the two parts 42 and 43, the hinge pins may be inserted into the holes and the center portions of the hinge pins may be moved past the adjacent ears until the center portions are Within the spaces between the adjacent ear and the hinge pin lug. The track part 43 is then swung in the clockwise direction as seen in FIG. 8 relative to the hub part 42 to bring the hinge pin lugs substantially into longitudinal alignments. As previously stated, in this position the ears 56 nad 71 overlie the center portions of the pins and prevent the pins from being withdrawn laterally out of the holes. While the two parts 42 and 43 are being held in this position, the two parts 42 and 43 are positioned on the shaft 27 and the part 42 is secured to the shaft 27. The two springs 58 may be connected to the ears 56 and 71 either before or after mechanism is positioned on the shaft. Once the mechanism has been mounted on the shaft 27, the part 43 cannot be swung to the position shown in FIG. 8 due to engagement of the side 61a with the shaft 27, and consequently the parts of the mechanism are interlockingly held in assembled relation while on the shaft 27.

The face 81 of the track part 43, which is away from the hub part 42 is substantially flat and smooth and is adapted to engage an actuating arm portion 82 of the switch when the centrifugal mechanism is in the at rest position, as shown in full lines in FIG. 1. With reference to FIGS. 9 to 15, the switch 40 comprises a case 83, a generally U-shaped spring clip 84, a movable member 86, and a stationary member 87. The case 83 includes two molded plastic halves 88 and 89 (FIG. 9) which are normally held together in assembled relation by the spring clip 84 which extends over three sides of the assembled halves 88 and 89. As shown in FIGS. 9 and 11, ridges 93 are provided on the outside of the two halves, the ridges forming channels 94 therebetween, which receive the arms of the spring clip 84, and which are closed at their inner ends by portions 95. The outer ends of the spring clip 84 are provided with curved clip portions 96 which snap over the portions 95 to releasably hold the clip on the halves 88 and 89 and the two halves together. Further, small rounded protrusions '97 (FIG. are formed on the side of the half 89, which engages the half 88, the protrusions 97 extending into mating depressions in the half 88 and thereby preventing the two halves from slipping relative to each other.

The switch 40 is secured to the end bell 22 of the motor by positioning the switch in an opening 101 (FIG. 1) formed in the outer radially extending face of the end bell 22. The end of the case opposite from the spring clip 84 has a radially extending flange 102 formed thereon, and the switch 40 is moved into the opening 101 until the flange 102 is tightly seated against an annular shoulder 103 formed on the end bell 22 within the opening 101. In this position, the outer face of the switch case is substantially flush with the outer radial face of the end bell 22. To hold the switch in place in the end bell, a fastening ring 104 (FIGS. 1 and 2) is pressed into the opening 101 over the flange 102. The fastening ring 104 includes a plurality of radially outwardly extending fingers 105 which tightly engage the inner periphery of the opening 101 when the ring 104 has been pressed into the opening to prevent the switch from accidentally falling out. The diameter of the outer edges of the fingers 105 is normally slightly greater than the inner diameter of the opening 101, so that the fingers 105 are bowed outwardly slightly as the fastening ring is pressed into the hole, and thus prevent the ring from falling out. To properly orient the switch 40 within the end bell, a pair of radially extending aligning lugs 106 (FIGS. 1, 2 and 9) are formed on the halves 88 and 89, the end bell 22 having slots which receive the lugs 106, thereby ensuring proper positioning of the switch.

By this construction, the switch 40 may be easily taken out of the motor for servicing and then reinstalled in the motor, or the switch 40 may be easily replaced by a new switch, without disassembly of the motor. To remove the switch 40, the ring 104 is first pried out of the opening 101 and then the switch 40 is pulled out through the opening 101. The switch case 83 may be tilted slightly as the switch is being removed so that the actuating arm portion 82 of the switch will clear the lower side of the opening 101. After repair or replacement of the switch, it is reinstalled in the motor by inserting it through the opening 101 until the flange 102 is seated on the shoulder 103, and then a new ring 104 is pressed into the opening 101 to hold the switch in place. The length of the switch from the shoulder 103 to the actuating arm portion 82 is of course such that the arm portion '82 is properly located to be engaged by the part 43 of the centrifugal mechanism.

The stationary member 87 and the movable member 86 are positioned within an opening 116 formed within the two halves, the movable member 86 including the actuating arm portion 82 which extends out of the case. The stationary member 87 comprises a square contact clip 117 (FIGS. 14 and and a contact 118 which is secured to the clip 117 as by welding. The clip 117 has two spring portions 119 and 120 which are punched out of the interior portions of the square contact member 117 and are bent upwardly therefrom. Two edges 121 (FIG. 15) of the contact member 117 are positioned in the grooves 122 (FIG. 10) formed in the two halves at one side of the opening 116 with the contact 118 facing toward the interior of the opening 116. As shown in FIG. 9, the contact clip 117 extends between the two halves 88 and 89 with one half of the contact member within each half.

The movable contact member 86 comprises the actuating arm portion 82 (FIGS. 1 and 10 to 12), a contact carrying arm portion 126, and a spring portion 127, the portions 82, 126 and 127 being formed from a single piece of metal. The member 86 is bent at 132 to form the arm portions 82 and 126, these two portions 82 and 126 making an angle of approximately (FIG. 12) and the contact carrying arm portion 126 having a contact 128 secured thereto as by welding. In the present instance, the distance of the contact 128 from the bend 132 is approximately equal to the length of arm portion 82, but it should be understood that any desired ratio of these two distances may be provided.

The spring portion 127 is formed in the center area of the movable member as by a punching operation and extends from a point in the arm portion 82 upwardly (FIG. 12) in the plane of the arm portion, past the bend 132 and is bent at 125a to extend parallel to the arm portion 126. The distance from the bend 132 to the point 125 is approximately equal to the distance from the bend 132 to the bend 125a.

With reference to FIG. 10, when the switch is assembled, the actuating arm portion 82 extends out of the case through an opening 131 formed in the case, the opening 131 communicating with the interior opening 116. Adjacent the lower end of the actuating arm portion 82 there is provided a rounded offset 137 (FIGS. 10 to 12) which is engageable by the face 81 of the track part 43 of the centrifugal mechanism. From the upper end of the bend 132 the arm portion 82 extends generally downwardly through the opening 131 and the contact carrying arm portion 126 extends toward the right as seen in FIG.

10 Within the opening 116. The contact 128 is located opposite the contact 118 of the stationary member 87. The spring portion 127 of the movable member extends upwardly from the bend 132 and horizontally into a narrow opening or slot 136 formed within the case above the main opening 116. When the two case halves are assembled with the movable member therein, the spring portion 127 is held relatively tightly within the slot 136, whereas the arm portions 82 and 126 are permitted limited movement. The bend 12511 in the spring portion 127 is received in a corner 135 formed in the main case opening 116.

The movable part 86 of the switch may either be supported entirely by the spring portion 127 being fixed in the slot 136, or it may be supported both in this manner and also by a lug engaging the bend 132. The latter construction is illustrated herein, wherein a rounded lug 133 (FIG. 10) is formed at the interior of the opening 116 and the bend 132 is positioned over the top of the lug. When such a lug is provided, its upper end is preferably notched down to a line so that the spring portion is free of the lug 133 but the bend 132 engages the lug 133.

To assemble the movable part 86 in one of the halves of the case such as the half 88, the upper end of the spring portion 127 is positioned in the slot 136 with the bend 125a in the corn-er 135 and the bend 132 is positioned over the lug 133. A rounded projection 138 is formed on the case at the margin of the opening 131 on the side of the opening opposite from the lug 133, and the actuating arm portion 82 is positioned in the opening 131 with the actuating arm portion 82 in engagement 'with the projection 138 when the switch contacts. are open, the projection 138 thus serving to limit the extent of movement of the arm portion 82 when the switch is opened. The stationary member 87 is positioned in the grooves 122 in the half 38, and the other half 89 of the case is positioned against the half 88, thus enclosing the stationary member 87 and the portions 126 and 127 of the movable member 86.

As shown in FIG. 10, the actuating arm portion normally bears against the projection 138 and the free end of the arm portion 126 normally rests on a ledge 141 formed on the two halves Within the opening 116, the two contacts 118 and 128 being out of engagement when in this position.

When pressure is applied on the offset 137, the actuating arm portion 82 and the arm portion 126 pivot in the counterclockwise direction as seen in FIG. 10 about the lug 133, the arm portion 126 swings upwardly and the contacts 118 and 128 move into engagement. After the contacts 118 and 128 have moved into engagement, continued counterclockwise movement of the actuating arm portion 82 causes the contact carrying arm portion 126 to bow upwardly slightly, such bowing causing the contact 128 to wipe and roll across the face of the contact 118, the contact 128 having a rounded surface for this purpose. The spring portion between the point 125 and the bend 125a also bows, and when the pressure on the offset 137 is released the force of the spring portion 127 returns the arm portions 82 and 126 to the solid line positions.

When a switch is provided without a lug 133, a force on the oifset 137 causes the arm portions 82 and 126 to swing in the clockwise direction about the bend 125a, the spring portion 127 flexing below the bend 125a. This construction has the advantages over a switch with the lug 133 of having less frictional drag on the movable member 86 and increased wiping action between the contacts 118 and 128.

The stationary contact clip 117 and the movable member 86 are both made of an electrically conductive metal, and electrical connections to the contacts 118 and 128 are made through bayonet type connectors 142 and 143 which respectively make electrical contact with the clip 117 and the spring portion 127 as shown in FIG. 10. Narrow openings approximately the width and thickness of the bayonet connectors are formed through the halves 88 and 89 of the case so that the connectors may be inserted through the openings. Small points 144 formed on the clip 117 and the spring portion 127 tightly engage the connectors 142 and 143 and establish firm electrical contact therebetween.

The switch may be assembled by first securing the contacts 118 and 128 to the clip 117 and movable part 86, respectively. The movable part and the stationary part are then assembled in one of the two housing halves and the other housing half is then assembled with the first housing half thereby enclosing the two contacts. The spring clip 84 is then fastened over the case halves in order to hold the halves in assembled relation, and the two bayonet connectors are then inserted into the respective slots in order to establish electrical connection with the two contacts. When the switch is fully assembled, the motor conductors (not shown) to be connected to the switch are drawn out of the motor through the opening 101 and attached to the bayonet connectors 142 and 143. The wires must of course be long enough for this purpose. Thereafter, the wires and the switch are inserted through the opening 101 formed in the end bell 22 and the fastening ring 104 is pressed into the opening 101 over the top of the switch to hold the switch in place in the end wall.

When the centrifugal mechanism has been assembled and installed on the rotor shaft 27 and the switch has been fastened in place in the end bell as previously explained, the switch contacts are normally held in electrical egnagement or contact by pressure of the track part 43 on the actuating arm portion '82 of the switch when the motor is at standstill and also when the motor is rotating at below a predetermined speed (solid line position in FIG. 1). When the motor is rotating at above the predetermined speed, the track part 43 is completely out of engagement with the arm portion 82 of the switch (dashed lines in FIG. 1), and the switch contacts are out of engagement. When in the solid line position, the springs 58 of the centrifugal mechanism exert sufiicient force on the track part to hold the track part in the at rest position and to pivot the actuating arm portion 82 and the contact carrying arm portion 126 against the force of the spring portion 127 and hold the switch contacts closed. When the mechanism is in this position, the arms of the pivot pins are substantially in longitudinal alignment, and since the spring portion 82 exerts only a longitudinally directed force on the track part of the centrifugal mechanism, there is no tendency of the spring portion to move the track part to the running position. Thus, the force exerted by the spring portion on the centrifugal mechanism cannot affect the calibration of the centrifugal mechanism. When the motor is energized and reaches a predetermined speed, the track part 43 of the centrifugal mechanism starts to swing radially outward, and once the track part has moved a slight amount in the radial direction, the arms of the hinge pins are no longer in longitudinal alignment. Consequently the longitudinally or axially directed force exerted by the switch on the track part 43 assists in moving the track part to the running position (shown in dashed lines in FIG. 1) until the track part 43 moves out of engagement with the switch actuating arm portion 82. In addition, the centrifugal force acting on the track part tending to move it radially outward gradually increase as the track part shifts radially outward due to the increased circle movement of the track part. Due to these factors, the track part of the centrifugal mechanism will remain in the at rest position until the predetermined speed is reached and then the track part will rapidly move outwardly with a snap action. When the track part reaches the running position it is completely out of engagement with the switch actuating arm portion 82 and the spring portion 127 moves the contact carrying arm portion 126 and the actuating arm portion 82 to the normal position shown in FIG. 10 thereby breaking electrical contact through the switch. If the switch is connected to the starting winding of the motor, this winding is deenergized when the switch opens. When the main winding of the motor is subsequently deenergized, the track part of the mechanism again swings radially and axially toward the switch and moves the arm portion 82 to the left, thereby reclosing the switch contacts.

It will be apparent from the foregoing description that an improved, economical and small size, centrifugal mechanism and switch construction has been provided. The two major parts of the centrifugal mechanism are formed by a molding operation with no machining or drilling required on the parts. These two parts of the centrifugal mechanism are easily assembled by inserting two hinge pins into the openings therefor and attaching the springs to the parts. Once the centrifugal mechanism has been positioned on a rotor chaft, the two molded parts and the hinge pins are held together in interlocking relation.

The switch of the assembly may also be inexpensively manufactured by molding the two halves of the case, forming the contact clip 117 from a single piece of metal by a punching operation, and forming the movable part 86 from another single strip of metal by a punching and bending operation. The parts of the switch may be easily assembled by installing the movable and stationary parts in one half of the switch case, enclosing the parts with the other half of the case, and then fastening the two parts of the case together using the spring clip 84. The switch is further advantageous in that relatively little actuating force is required to move the switch between its positions, the exact amount of the spring force being determined by the design of the spring portion 127. In a construction where the distance of the contact 128 from the bend 132 is approximately equal to the distance from the bend 132 to the otfset 137 which is engaged by the switch, the contact 128 will move substantially the same distance as the portion 137. Therefore, since the contacts are relatively close together even when the switch is open, the track part of the pivotal mechanism need move only a short distance in order to actuate the switch from one of its two positions to the other position. In addition to the foregoing advantages, the switch permits a long overtravel of the track part of the centrifugal mechanism since such overtravel will simply flex the actuating arm' portion 82.0f the switch and the size of the opening 131 9 is such as to permit considerable flexing of the arm portion 82.

Since the actuating arm portion 82 moves only a short distance when the switch is actuated between its two positions, it is possible for the track part 43 to move completely out of engagement with the arm portion 82. This is advantageous because the track part 43 and the arm portion 82 are out of engagement when maximum wear would otherwise occur, which is at running speed. Further, the switch contacts move completely to the open position and are not held intermediate the open and closed positions due to engagement of the arm portion 82 by the track part 43. However, even if the switch should fail, such failure usually being due to contact arcing or wear at the oiTset 137, the switch may be easily replaced without disassembly of the motor. Thus, the switch is mounted within the motor housing and not in a separate housing external to the motor as in some constructions. Nevertheless the switch may be easily replaced when necessary without disassembly of the motor.

I claim:

1. A centrifugal mechanism for use with a r tatable shaft, comprising a first part, a second part, hinge means, including a removable hinge part, connecting said second part to said first part for enabling swinging movement of said second part relative to said first part between first, second and third positions, said first position being obtained when said parts are mounted on the shaft and are rotating with the shaft at above a predetermined speed, said second position being obtained when said parts are mounted on said shaft and are at standstill or are rotating below said predetermined speed, and said third position being obtained only when said parts are off of said shaft, said second part including means adapted to engage the shaft to prevent said second part from moving to said third position when said parts are mounted on the shaft, and abutment means formed on said first and second parts and being in overlying relation with said removable hinge part to prevent removal of said hinge part when said second part is in said first and second positions, said abutment means being out of overlying relation with said hinge part only when said second part is in said third position.

2. Apparatus as in claim 1, wherein said first and second parts are of molded plastic, and said molded plastic second part includes a metal Weight embedded therein.

3. Apparatus as in claim 1, and further including spring means connected between said first and second parts for urging said parts relative to each other from said first position toward said second and third positions, said spring means being connected to said abutment means on said first and second parts.

4. Apparatus as in claim 1, wherein said removable hinge comprises a pair of U-shaped hinge pins, the center portions part of said pins extending between said first and second parts, and said abutment means overlying said center portions of said hinge means when said parts are in said first and second positions but being displaced from said center portions when said parts move to said third position.

References Cited UNITED STATES PATENTS 1,897,405 2/1933 Thompson 200- 2,039,568 5/1936 Tamsitt.

2,188,559 1/1940 Taylor 20080 2,573,514 10/1951 Turner.

2,611,602 9/1952 Rosebraugh 73538 2,797,080 6/1957 Johnson 73538 3,058,355 10/1962 Larsh 73535 3,194,914 7/1965 Brown 200--80 3,209,093 9/1965 Simpson 20080 3,244,832 4/1966 Schaefer 200-80 3,290,463 12/1966 Johnson 20076 ROBERT K. SCHAEFER, Primary Examiner DAVID SMITH, JR., Assistant Examiner US. Cl. X.R. 

